Mixer impeller

ABSTRACT

Mixer impeller blades of hat-section cross section are secured to bracket arms which project radially from an impeller shaft. A cover plate extends across the hat-section cavity and is fastened to opposite brim portions, forming a flat forward face for the impeller blade. The bracket arm is inclined, relative to the plane of the axis of rotation of the impeller shaft, so that the flat forward face of the hat-section impeller blade is also inclined. The leading or forward brim portion of the blade is preferably narrower than the trailing brim portion to accommodate for the greater forces of stress which are imposed on the leading edge.

United States Patent [1 1 Quinn MIXER IMPELLER [75] Inventor: Jerome B. Quinn, Kennett Square,

[73] Assignee: Philadelphia Gear Corporation,

King of Prussia, Pa.

[22] Filed: Apr. 11, 1974 [21] Appl. No.: 460,105

Related US. Application Data [63] Continuation-impart of Ser. No. 359,421, May 11,

Bergen 416/210 June 3, 1975 12/1971 Wooden ..416/210 6/1974 Quinn ..4l6/210 [57] ABSTRACT Mixer impeller blades of hat-section cross section are secured to bracket arms which project radially from an impeller shaft. A cover plate extends across the hat-section cavity and is fastened to opposite brim portions, forming a flat forward face for the impeller blade. The bracket arm is inclined, relative to the plane of the axis of rotation of the impeller shaft, so that the flat forward face of the hat-section impeller blade is also inclined. The leading or forward brim portion of the blade is preferably narrower than the trailing brim portion to accommodate for the greater forces of stress which are imposed on the leading edge.

18 Claims, 7 Drawing Figures PATENTEDJUH3 1925 3,887,300

SHEET 1 MIXER IMPELLER CROSS REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of my co-pending application Ser. No. 359,421, filed May 11, I973 entitled Mixer Impeller Blade. This application was allowed Jan. 10, 1974 and is now U.S. Pat. No. 3,8l6,024, issued June II, 1974.

BACKGROUND OF THE INVENTION The present invention relates to impeller blades, and primarily to impeller blades for use in mixers.

Mixer impeller blades of the prior art have ordinarily been made of relatively heavy steel plate having a longitudinal reinforcing rib welded to the back surface thereof.

SUMMARY OF THE INVENTION The object of the present invention is to provide a mixer blade of lighter weight but substantially equal strength to that of the prior art and so constructed as to reduce the amount of welding and the distortion which welding generates.

The foregoing object is achieved in accordance with the present invention, by providing a hat section of relatively thin steel and covering the cavity of the crown portion with a thin flat plate spot welded to the brim portion. The radially inward end of the hat-section blade is secured to bracket arms which project radially from the impeller shaft at an inclination relative to the plane of the rotational axis of the impeller shaft. When mounted, the flat forward surface of the hat-section impeller blade is also inclined relative to the axis of the impeller shaft. Preferably, the brim portion which corresponds to the leading edge of the inclined hat-section impeller has a lesser width than does the brim portion at the trailing edge, thereby to accommodate the greater stress forces which are imposed on the leading edge portion of the impeller blade. Structural means of improved strength are employed for securing the hatsection impeller blade to the bracket arm on the impeller shaft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing four impeller blades extending radially from the impeller shaft.

FIG. 2 is a slightly enlarged view of the undersurface or forward face of the impeller blade.

FIG. 3 is a side elevation, in section, taken along the line 3-3 of FIG. 2.

FIG. 4 is an end elevation, in section, taken along the line 44 of FIG. 2.

FIG. 5 is an end elevation taken along the line 55 of FIG. 1.

FIG. 6 is a plan view of the forward face ofa modified form of impeller blade.

FIG. 7 is an end elevation looking along the line 7-7 of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, an impeller shaft S has a hub secured thereto, as by key and keyway not shown. Projecting radially from hub 20 are bracket arms 21. In FIG. 1, four such bracket arms 21 are shown, at 90 spacing. The bracket arms 21 are angularly inclined,

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relative to the plane of the rotational axis of the impeller shaft S. The angle of inclination varies according to the particular mixer needs. As one example, an angle of 32 may be used.

Secured to the four bracket arms 21, by means which will be described later, are four impeller blades 10, each of which is similar in construction. Accordingly, it will be necessary to describe but one of the blades.

As seen in FIGS. 1-5, each of the impeller blades 10 has a hat-section cross section. The hat section includes a crown 12, opposite brim portions 14 and 114, and inclined sidewalls 13 and 113, forming between the sidewalls the hat-section cavity 15. A flat cover plate 16 extends across the hat-section cavity 15 and is secured to the opposite brim portions 14 and 114, as by spot weld- As viewed in FIG. 1, the direction of rotation of the impeller shaft S is clockwise, as is indicated by the arrow. When the impeller blades 10 are driven through the liquid or other mixture in the mixer, the leading edge portion of the inclined impeller blade 10 is the brim portion 14. It has been found that the stress forces on the leading portion 14 are greater than on the trailing portion 114 and, in view thereof, it is desirable to make the brim portion 14 of lesser width than the trailing brim portion 114. The center line of the crown portion 12 of the impeller blade 10 lies in the plane of the rotational axis of the impeller shaft S. Thus, the area of the leading face of the impeller blade 10 on the leading side of the center line of the crown portion is less than on the trailing side. This is preferred in view of the greater stresses which are impressed on the leading edge portion of the impeller blade.

The means for attaching the impeller blades 10 to the bracket arm 21 will now be described. The preferred means of attachment is illustrated in FIGS. 1-4. A modified form of attachment is illustrated in FIGS. 6-7. The preferred form will be described first.

Referring now to FIGS. 1-4, a reinforcing plate 22 is placed on the outer surface of the crown 12 at the radially inward end thereof. While not essential, for optimum strength, an insert 32 of heavier metal than cover plate 16 may be welded at the inward end of cover plate 16. A pair of elongated load-bearing channel members 33 are inserted in parallel relation into the cavity 15 at the radially inward end thereof. As seen in FIG. 2, these load-bearing channel members 33 extend beyond the limit of the insert 32 and the reinforcing plate 22. Four load-bearing bushings 35 are placed within the load-bearing channel members 33 for receiving the four bolts 36. These bolts 36 are used to secure the bracket arm 21 to the impeller blade 10. As best seen in FIG. 4, the bracket arm 21 and the reinforcing plate 22 are on opposite sides of the hat-section cavity 15. Between the bracket arm 21 and plate 22, are the insert 32, the load-bearing channel members 33, the load bearing bushings 35, and the crown 12.

The means for attaching impeller blade 10 to bracket arm 21, illustrated in FIGS. 1-4 and just described, provide the structural strength necessary to withstand the stress forces which are placed on the impeller blade 10 during rotation of the blade through the liquid or other mixture in the mixing tank.

Where the stresses on the impeller blade 10 are not expected to be as large, a modified form of attachment may be employed. Such a modified form is illustrated in FIGS. 6 and 7. As there illustrated, the bracket arms 121 are modified to include an upstanding rib portion 122 which is received within a slot provided in the cover plate 116. The bracket arm 121 is inserted into the cavity 15 between the cover plate 116 and the crown 12. Reinforcing plate 22 is employed on the outer surface of crown 12. The load-bearing channel members 33 and the load-bearing bushings 35 are omitted, and the bolts 36 are inserted through the cover plate 116, bracket arm 121, crown 12 and reinforcing plate 22.. Spacer washers 37 are inserted between the cover plate 116 and the bracket arm 121.

In both the preferred form (FIGS. 1-5) and the modified form (FIGS. 6-7), a vertical plate is inserted at the radially outward end of the hat-section blade between the crown 12 and the cover plate 16, 116. This plate is identified 38 in FIGS. 1-5 and 138 in FIGS. 6-7. This plate serves as a reinforcing structural member. It also serves as a partial barrier to limit the flow of mixer liquid through the cavity 15. In the embodiment of FIGS. 6-7, an additional barrier is inserted near the inward end portion of the cavity 15. This additional barrier, identified 139 in FIGS. 6-7, is a total barrier across cavity 15, and prevents flow of mixer liquid through the cavity 15 of the hat-section blade.

Without intending to be limited to the values given, an impeller blade according to the present invention may have the following dimensions and values:

The hat-section impeller blade may have a length of 45 /8 inches and a width of 29 5/16 inches, and may be formed of 3/16 inch thick stainless steel, number 316L. The depth of the hat-section cavity 15 may be 2 9/16 inches. The width of the crown 12 may be 8 inches. The dimension from the center axis of the hat-section blade to the edge of the narrow brim 14 may be 13 12/16 inches, and the dimension from the center axis to the edge of the broad brim 114 may be 15 9/16 inches. The cover plate 16 may have a width of 24 inches, and may be of 10-gauge (.135) stainless steel. The sidewalls 13 and 113 may be at 45 angles relative to the plane of the cover plate 16.

The reinforcing plate 22 on the surface of crown 12 at the inward end of the blade may be A inch thick stainless steel and may be 15 inches long and 8 inches wide. Insert 32 in cover plate 16 may be A inch thick stainless steel and may be 1 1 /2 inches long and 14 /8 inches wide. The channel members 33 may be of 10- gauge (.135) stainless steel, and may have a length of 18 inches and a total width of 5 inches. The width of the channel itself may be 2 inches.

What is claimed is:

1. In combination:

a. an impeller shaft having an axis of rotation;

b. bracket arms secured to said shaft and extending radially outwardly therefrom;

c. impeller blades attached to said bracket arms, said impeller blades comprising:

c-l. a hat section having a crown, opposite brim portions, and side walls inter-connecting said crown and opposite brim portions and forming a hat-section cavity;

c-2. a flat cover plate secured to opposite brim portions and extending across said hat-section cavity and forming, with said brim portions, a forward flat face for said impeller blade;

d. and means connecting the radially-inward end portion of said impeller blade to said bracket arms in such disposition that the forward flat face of said impeller blade is inclined relative to the plane of the rotational axis of said impeller shaft.

2. The combination according to claim 1 wherein:

a. said impeller shaft bracket arms are inclined relative to the plane of the rotational axis of said shaft;

b. said means for connecting said impeller blades to said bracket arms comprise:

b-l. a flat reinforcing plate secured to the outer surface of said crown at the radially inward end thereof;

b-2. bolt means extending through said bracket arm, cover plate, hat section cavity, crown, and reinforcing plate.

3. The combination according to claim 2 wherein load-bearing bushings are inserted into said cavity between said cover plate and said crown and through which said bolt means pass.

4. The combination according to claim 3 wherein a barrier plate is provided at the radially outward end of said impeller blade between said crown and cover plate.

5. The combination according to claim 1 wherein:

a. the brim portion on one side of said hat-section cavityhas a lesser width than the brim portion on the opposite side of said hat-section cavity.

6. The combination according to claim 5 wherein:

a. the brim portion having the lesser width is at the leading edge of said impeller blade when said inclined impeller blade is driven rotationally about the rotational axis of said shaft.

7. The combination according to claim 1 wherein reinforcing channel members are inserted into the hatsection cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.

8. The combination according to claim 7 wherein loadbearing bushings are inserted into said channel members.

9. The combination according to claim 8 wherein bolt means extend through said bracket arms, cover plate, bushings, and crown.

10. The combination according to claim 5 wherein reinforcing channel members are inserted into the hatsection cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.

11. The combination according to claim 10 wherein load-bearing bushings are inserted into said channel members.

12. The combination according to claim 11 wherein bolt means extend through said bracket arms, cover plate, bushings, and crown.

13. The combination according to claim 2 wherein the brim portion on one side of said hat-section cavity has a lesser width than the brim portion on the opposite side of said hat-section cavity.

14. The combination according to claim 13 wherein reinforcing channel members are inserted into the hatsection cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.

15. The combination according to claim 14 wherein load-bearing bushings are inserted into said channel members.

16. The combination according to claim 15 wherein said bolt means extend through said bracket arm, cover and cover plate.

18. The combination according to claim 1 wherein said bracket arms are inserted into said hat-section cavitv. 

1. In combination: a. an impeller shaft having an axis of rotation; b. bracket arms secured to said shaft and extending radially outwardly therefrom; c. impeller blades attached to said bracket arms, said impeller blades comprising: c-1. a hat section having a crown, opposite brim portions, and side walls inter-connecting said crown and opposite brim portions and forming a hat-section cavity; c-2. a flat cover plate secured to opposite brim portions and extending across said hat-section cavity and forming, with said brim portions, a forward flat face for said impeller blade; d. and means connecting the radially-inward end portion of said impeller blade to said bracket arms in such disposition that the forward flat face of said impeller blade is inclined relative to the plane of the rotational axis of said impeller shaft.
 1. In combination: a. an impeller shaft having an axis of rotation; b. bracket arms secured to said shaft and extending radially outwardly therefrom; c. impeller blades attached to said bracket arms, said impeller blades comprising: c-1. a hat section having a crown, opposite brim portions, and side walls inter-connecting said crown and opposite brim portions and forming a hat-section cavity; c-2. a flat cover plate secured to opposite brim portions and extending across said hat-section cavity and forming, with said brim portions, a forward flat face for said impeller blade; d. and means connecting the radially-inward end portion of said impeller blade to said bracket arms in such disposition that the forward flat face of said impeller blade is inclined relative to the plane of the rotational axis of said impeller shaft.
 2. The combination according to claim 1 wherein: a. said impeller shaft bracket arms are inclined relative to the plane of the rotational axis of said shaft; b. said means for connecting said impeller blades to said bracket arms comprise: b-1. a flat reinforcing plate secured to the outer surface of said crown at the radially inward end thereof; b-2. bolt means extending through said bracket arm, cover plate, hat section cavity, crown, and reinforcing plate.
 3. The combination according to claim 2 wherein load-bearing bushings are inserted into said cavity between said cover plate and said crown and through which said bolt means pass.
 4. The combination according to claim 3 wherein a barrier plate is provided at the radially outward end of said impeller blade between said crown and cover plate.
 5. The combination according to claim 1 wherein: a. the brim portion on one side of said hat-section cavity has a lesser width than the brim portion on the opposite side of said hat-section cavity.
 6. The combination according to claim 5 wherein: a. the brim portion having the lesser width is at the leading edge of said impeller blade when said inclined impeller blade is driven rotationally about the rotational axis of said shaft.
 7. The combination according to claim 1 wherein reinforcing channel members are inserted into the hat-section cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.
 8. The combination according to claim 7 wherein loadbearing bushings are inserted into said channel members.
 9. The combination according to claim 8 wherein bolt means extend through said bracket arms, cover plate, bushings, and crown.
 10. The combination according to claim 5 wherein reinforcing channel members are inserted into the hat-section cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.
 11. The combination according to claim 10 wherein load-bearing bushings are inserted into said channel members.
 12. The combination according to claim 11 wherein bolt means extend through said bracket arms, cover plate, bushings, and crown.
 13. The combination according to claim 2 wherein the brim portion on one side of said hat-section cavity has a lesser width than the brim portion on the opposite side of said hat-section cavity.
 14. The combination according to claim 13 wherein reinforcing channel members are inserted into the hat-section cavity at the radially inward end of said impeller blade, said channel members having a height corresponding to the height of said hat-section cavity.
 15. The combination according to claim 14 wherein load-bearing bushings are inserted into said channel members.
 16. The combination according to claim 15 wherein said bolt means extend through said bracket arm, cover plate, channel member and bushing, crown and reinforcing plate.
 17. The combination according to claim 2 wherein a barrier plate is provided near the radially inward end portion of said hat-section cavity between said crown and cover plate. 